Following surgery on the knee it is common for the knee to be immobilized during a period of recovery. Likewise, recovery from strains or sprains is frequently enhanced by immobilization of the knee joint. In other situations, knee immobilization may be provided merely as support for weakened knees for various causes. The primary function of a knee immobilizer orthopedic appliance is to render the knee joint immobile. To appropriately perform this function, the appliance should be capable both of conforming closely to the contour of the leg above and below the knee and capable of accommodating the several protruberances associated with the knee itself. The appliance further should be capable of being relatively tightly bound about the leg in the area above the knee and below the knee and means must be provided for rigidifying the appliance to the extent that the knee joint is immobilized.
Knee movements are primarily anterior and posterior flexion of the leg about the knee joint so that the primary immobilization is directed to prevention of such flexion. Commonly, however, immobilization anticipates protection against lateral and medial flexion of the knee joint. Therefore, it is desirable in a knee immobilizer that all four flexion movements be prevented by the appliance.
Heretofore it has been common to fabricate a knee immobilizer of a relatively soft conformable body member which has one or more pockets provided at selected locations about the circumference of the appliance as it is applied to the knee and oriented along the extended leg. Stays are inserted in such pockets. These stays are referred to also at time as stabilizers or rigidifiers or stiffeners. Commonly these take the form of elongate bars that are inherently rigid, typical of these stays being aluminum or spring steel strips. Other stays have been proposed for knee immobilizer-type appliances that include ribs for enhancing the rigidity of the aluminum strips. In certain instances, it has been proposed that multiple stays be provided to insure the desired rigidity of the appliance when applied to the leg.
One of the major problems with inherently rigid stays resides in the fact that one of the most desirable locations of a stay in a knee immobilizer is directly along the medial and/or along the lateral side of the leg. A stay positioned along the lateral side of the leg places the stay directly over the peroneal nerve that originates at the lumbar fourth and fifth level and comes down around the neck of the fibula and down the lateral side of the calf. Thus, the peroneal nerve in the area of the knee is positioned between the head of the fibula and the stay of the knee immobilizer. In this position, the peroneal nerve is subject to damage as by compression or entrapment, the most frequent cause of nerve damage being compression which can result from improperly applied or ill fitting or ill designed immobilizers, etc.
Peroneal nerve damage can be temporary or permanent depending upon the circumstances of the damage. Foot drop, which is manifested by a characteristic gait, results from peroneal nerve damage. The foot flops down and slides forward because of a patient's inability to lift the foot due to the peroneal nerve damage.
It is therefore an object of the present invention to provide an orthopedic appliance particularly suitable for knee immobilization in which the appliance provides protection against peroneal nerve damage while providing the desired immobilization of the knee.
It is another object of the present invention to provide an improved stay for a knee immobilizer.
It is another object of the invention to provide a stay for a knee immobilizer wherein the stay is capable of conforming to the contour of the leg and knee and simultaneously capable of imparting the desired rigidity to the knee immobilizer.
It is another object of the present invention to provide a stay for a knee immobilizer wherein the stay provides protection for the popliteal fossa.